Reverse Hip Prosthesis System

Abstract

The articulated reverse hip prosthesis includes an acetabular cup with an opening in the cup's central portion, which is implanted into the acetabular cavity. The opening has a circular, extended wall that protrudes into the cup's recess a distance at least equal to the diameter of the opening. The cup's inward extension provides a female Morse taper suitable for accepting the male Morse taper post of the acetabular ball. After implantation of the acetabular cup, the surgeon can simply secure the cup to the acetabular bone using several screws, without the interference of a central peg (as with previous implants). The femoral ball is then attached to the cup via the central Morse taper.

Description

[Background technology]

[0001] The present invention relates to hip joint prostheses, and more particularly to an articulated reverse hip joint prosthesis comprising an acetabular component having a removable central Morse taper central peg for facilitating the insertion of multiple locking acetabular screws.

[0002] While it is recognized that some hip implants have been in common use for many years, there is a need for a design that facilitates the insertion of multiple locking screws at different angles without interfering with the central post.

[0003] The present invention provides a novel articulated reverse hip prosthesis that incorporates an acetabular ball and a central post. The post is rigidly and concentrically attached to the central apical circular opening of the acetabular cup and secured via a Morse taper. The acetabular cup is then inserted and driven into an acetabular socket constructed in the pelvis by the surgeon and secured by one or more interlocking screws that pass through one or more openings in the acetabular cup. In some embodiments, these interlocking screws are replaced with biocompatible absorbable studs. A central post is then inserted into the central apical opening, firmly driven, and held in place via a Morse taper. Next, the femoral component is inserted and driven into the hollowed-out femoral canal, prepared by the surgeon using an appropriately sized reamer. Notably, removing the central post, which can interfere with proper angled screw insertion, facilitates the insertion of multiple interlocking screws. During ambulation, the edge or lip of the articulating femoral cup fits and slides concentrically within the interlocking space located between the acetabular ball and the acetabular cup. As will be apparent to those skilled in the art, the geometric configuration of the present invention makes the femoral cup very difficult to dislocate, even with increased range of motion, because it is constrained within the fixed space between the acetabular cup and the acetabular ball.

[0004] Furthermore, because the articular surfaces of the two components are in full contact 100% of the time, it is clear that this improves weight distribution, reduces wear on the contact surfaces, and reduces the number of wear particles released into the joint. The latter is highly detrimental to the proper function of the joint and often leads to osteolysis and loosening of the implant components. A novel feature of the present invention is that the central post is removable and does not mechanically impinge or interfere with the insertion of the interlocking fixation screws. The result is a novel reverse hip implant that, when considered alone or in any combination, is not anticipated, manifested, suggested, or even inferred from conventional hip prostheses.

[0005] Various other objects, features, and advantages of the present invention will become better understood by considering it in conjunction with the present accompanying drawings, in which like reference characters indicate the same or similar elements throughout the several views. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view of an articulated reverse hip acetabular cup with a central Morse taper opening. [Figure 2] FIG. 2 is a cross-sectional view of an articulated reverse hip acetabular cup with a central post inserted into a Morse tapered opening. [Figure 3] FIG. 3 is a perspective view of a monoblock acetabular ball and tapered central post. [Figure 4] FIG. 4 is a cross-sectional view of an assembled articulated reverse hip implant. [Figure 5] Figure 5 is a cross-sectional view of the acetabular cup impactor. DETAILED DESCRIPTION OF THE INVENTION

[0007] Turning now to the drawings, in which like reference numerals refer to like elements throughout the several views, the accompanying drawing illustrates an articulated reverse hip prosthesis comprising a hemispherical acetabular cup (4) with smooth concave and convex non-articular surfaces. The convex non-articular surface provides a porous surface with multiple irregularities and microvoids to allow for bone ingrowth. Additionally, the acetabular cup (4) is provided with one or more holes (2) at different locations for use with one or more interlocking screws (not shown). The concave hemispherical surface of the acetabular cup (4) provides a central, female, tapered opening (1) that extends into the interior of the acetabular cup's concave space. The opening is tapered to comfortably accept a male, tapered central post (6). The acetabular ball (5) is rigidly attached to the central post either as a monoblock or using a Morse taper.

[0008] In one embodiment, the acetabular cup comprises at least two recesses (3) located diametrically opposed near the equatorial edge of the cup near the periphery of the acetabular cup and used to secure a hand-held impactor for impacting the cup into the acetabular-pelvic cavity prepared by the operating surgeon.

[0009] In another embodiment, the unitary acetabulum may include two or more recesses for receiving fixation pins, and the recesses may have a square or oval shape.

[0010] Figure (4) shows an acetabular cup with an acetabular ball hammered into the central opening (1) and a central post (6). A femoral metal cup (9) has a tapered stem (10) and a polyethylene lining (8) that makes comfortable contact with the acetabular ball (5).

[0011] In one embodiment, the articular surface of the femoral cup comprises high molecular weight polyethylene of varying thicknesses, but not less than 4 mm. In another embodiment, the lining may be porcelain, ceramic, or a metal alloy. Modifications to the design to meet the needs of different sizes will be apparent to those skilled in the art.

[0012] Referring to Figure 4, when the metal femoral cup 8 and its polyethylene lining 9 articulate on the acetabular ball 5, the rim of the femoral cup moves in and out of the hemispherical articulating space 7, and the articular surface of the femoral cup maintains the same contact area as the acetabular ball throughout the range of motion. In other words, 100% of the articular contact area of ​​the femoral cup is maintained throughout the range of motion.

[0013] Reference is now made to FIG. 5, which illustrates in detail the acetabular cup handheld impactor. The handheld impactor has a truncated hemisphere (12) in the shape of a frustum and a lip that extends beyond the outer periphery of the handheld impactor, thereby resting on the beveled rim of the acetabular cup. The distal surface of the hemisphere does not contact the central Morse taper-shaped central opening (6). An upwardly extending central shaft (11) has a driving handle at its proximal end and a distal end that is firmly embedded in the body of the polyethylene impactor (12). A metal sleeve (19) disposed around the central shaft (11) has a cone-shaped distal end. The sleeve is slidably biased distally via a spring (17) located in the space between the sleeve (19) and the central shaft (11). To keep the acetabular cup securely attached to the impactor, two fixation pins are positioned in diametrically opposed channels (20) and are forced inward and held retracted via springs (16). When sleeve (19) is forced downward by springs (17), distal cones (18) force fixation pins 14 into recesses (3) in the acetabular cup, thereby securing the acetabular cup to the hand-held impactor during the impaction process.

[0014] In another embodiment of the present invention, the acetabular cup has multiple holes for the insertion of multiple fixation screws specifically designed for use in revision hip replacement surgery.

[0015] Revision is a surgical procedure to remove an existing implant. This most frequently requires removal of the acetabular cup and is associated with a high level of morbidity. Removal of a previously implanted acetabular cup can be surgically very difficult, especially if the cup has metal beads attached for bone ingrowth. In these cases, removal is also accompanied by iatrogenic bone loss, making it difficult to insert another conventional acetabular cup.

[0016] An important feature of the present invention is that the acetabular cup can be positioned and driven in place without a central post interfering with the placement of multiple screws at different angles, such as during revision surgery. Following insertion of the acetabular cup, the central post and acetabular ball are properly driven into the central Morse taper. As noted above, there are significant advantages to using multiple screws during revision hip arthroplasty, where the quality of the acetabular bone dictates the number and location of fixation screws. The central post limits the exposure and prevents placement of said fixation screws.

[0017] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a new and improved articulated reverse hip prosthesis system in which a metal acetabular cup has a removable central post to allow for the insertion of multiple fixation screws, such as during revision hip replacement surgery or in cases of complex fractures requiring pelvic reconstruction.

[0018] With respect to the above description, it is understood that the optimum dimensional relationships of the components of the present invention, including variations in size, material, shape, form, function, method of operation, assembly, and use, will be readily apparent to those skilled in the art, and that all equivalent relationships to those shown in the drawings and described in the specification are intended to be encompassed by the present invention. Accordingly, the foregoing is considered to be merely illustrative of the principles of the present invention. Moreover, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, but rather to resort to all suitable modifications and equivalents within the scope of the present invention.

Claims

1. a one-piece acetabular cup having a convex non-articular surface for attachment to an acetabular socket of a pelvis and a concave surface opposite the convex non-articular surface, the concave surface having a central opening; an acetabular ball rigidly attached to the peg; a femoral cup rigidly secured to the proximal end of the femoral implant; a handheld impactor for inserting the acetabular cup into the prepared acetabular bone cavity. A reverse hip prosthesis system.

2. 10. The reverse hip prosthesis system of claim 1, The concave surface of the acetabular cup is hemispherical and has a central apical opening. A reverse hip prosthesis system.

3. 3. The reverse hip prosthesis system of claim 2, The central opening is tapered to provide a female Morse taper A reverse joint prosthesis system.

4. 3. The reverse joint prosthesis system of claim 2, The Morse taper central opening has a circular wall having a height not exceeding 1.5 times the diameter of the base of the central opening. A reverse joint prosthesis system.

5. 10. The reverse hip prosthesis system of claim 1, The outer wall of the central opening flares proximally and smoothly transitions to the inner wall of the acetabular cup. A reverse joint prosthesis system.

6. 10. The reverse hip prosthesis system of claim 1, the convex surface of the acetabular cup is hemispherical; The concave surface of the cup is also hemispherical. A reverse joint prosthesis system.

7. 6. The reverse hip prosthesis system of claim 5, The one-piece acetabular cup has at least two recesses for receiving fixation pins. A reverse joint prosthesis system.

8. 8. The reverse hip prosthesis system of claim 7, The diametrically opposed recesses are located near the equatorial edge of the cup. A reverse joint prosthesis system.

9. 8. The reverse hip prosthesis system of claim 7, The diametrically opposed recesses are circular, oval or polygonal in shape. A reverse joint prosthesis system.

10. 10. The reverse hip prosthesis system of claim 1, The handheld impactor comprises: A metal cylinder, a central metal core with a handle at its proximal end; a spring attached to the central metal core for biasing the metal cylinder distally; a polyethylene frustum for preventing contact with the central Morse extension during impaction; The polyethylene frustum has at least two diametrically spring-loaded locking pins. A reverse joint prosthesis system.

11. 11. The reverse hip prosthesis system of claim 10, The distal end of the metal cylinder is tapered to provide a camming action that causes the fixation pin to expand outwardly into diametrically opposed equatorial recesses in the acetabular cup. A reverse joint prosthesis system that

12. 11. The reverse hip prosthesis system of claim 10, The fixing pins are positioned in diametrically opposed cylindrical channels and are forced inward via springs. A reverse joint prosthesis system that

13. 10. The reverse hip prosthesis system of claim 1, The handheld impactor device is fabricated from metal, metal alloy, or composite material A reverse joint prosthesis system.

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